B9 Alloy Research Articles

Lattice distortion enabling enhanced strength and plasticity in high entropy intermetallic alloy

Intermetallic alloys have traditionally been characterized by their inherent brittleness due to their lack of sufficient slip systems and absence of strain hardening. However, here we developed a single-phase B2 high-entropy intermetallic alloy that is both strong and plastic. Unlike conventional intermetallics, this high-entropy alloy features a highly distorted crystalline lattice with complex chemical order, leading to multiple slip systems and high flow stress. In addition, the alloy exhibits a dynamic hardening mechanism triggered by dislocation gliding that preserves its strength across a wide range of temperatures. As a result, this high-entropy intermetallic circumvents precipitous thermal softening, with extensive plastic flows even at high homologous temperatures, outperforming a variety of both body-centered cubic and B2 alloys. These findings reveal a promising direction for the development of intermetallic alloys with broad engineering applications.

Cracking and Precipitation Behavior of Refractory BCC–B2 Alloys Under Laser Melting Conditions

Cracking and Precipitation Behavior of Refractory BCC–B2 Alloys Under Laser Melting Conditions

Evaluation of the Combustion Properties and Catalytic Activity of MgAlB Energetic Ternary Particles

ABSTRACT Boron powder possesses significant potential for use as a combustible agent in energetic materials, owing to its superior combustion thermodynamic properties. However, the powder’s tendency to form an oxide layer on its surface results in delayed ignition, reduced combustion efficiency, and compromised energy advantage. To enhance the ignition and combustion properties of boron powder, we prepared boron-based energetic composites containing flammable metals (MgxAl1-xB2) through high-temperature sintering. These were then characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS). The combustion heat of these alloy powders were measured using an oxygen bomb calorimeter, while their catalytic performance on the thermal decomposition of ammonium perchlorate (AP) was analyzed using differential scanning calorimetry (DSC) and differential thermal analysis (DTA). The results indicate that compared with boron, the MgxAl1-xB2 powders are more flammable, require less oxygen, exhibit a higher combustion efficiency and exothermic advantage. Especially, the Mg0.9Al0.1B2 and MgB2 alloy exhibit optimal combustion heat values of 39,094.92 and 37,693.90 J·g−1, respectively. They significantly enhance the thermal decomposition of AP and reduce the activation energy by over 20%.

Strength of Disordered and Ordered Al‐Containing Refractory High‐Entropy Alloys

Body‐centered‐cubic refractory high‐entropy alloys are promising for high‐temperature structural applications due to their exceptional properties, particularly in terms of yield strength at elevated temperatures. For certain alloy systems, such as Mo–Ti–Cr–Al, both disordered (A2) and ordered (B2) crystal structures are possible. In this particular system, a solid‐state transformation from A2 to B2 during cooling occurs. For Al concentrations above ≈10 at%, B2 order is obtained from the transformation temperature down to room temperature (RT), while A2 is stable above RT below the critical Al content. Herein, two alloys from the Mo–Ti–Cr–Al system close to the transition between A2 and B2 are investigated. Nanoindentation tests reveal that the magnitude of strain rate sensitivity for both alloys is small compared to classical alloys, however, significantly temperature dependent up to the strength plateau temperatures. The yield strength plateau, which is insensitive to the strain rate, is observed at temperatures exceeding 573 K. Modeling of solid solution strengthening reproduces the experimental data in the Al‐lean A2 alloys. However, the observed discontinuous increase of strength in the Al‐rich B2 alloys can only be rationalized by the appearance of B2 order and to no significant other obvious strengthening mechanisms.

Unexpected effects on creep resistance of an extruded Mg-Bi alloy by Zn and Ca co-addition: Experimental studies and first-principles calculations

In the present work, a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equivalent atom fraction with Bi. Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s. Room temperature mechanical properties and creep behaviors at 423 K were investigated. The results show that Zn and Ca co-addition shows little influence on average grain size and texture intensity but changes the dispersive Mg3Bi2 into Mg2Bi2Ca particles in different sizes and a lower density. Twinning is largely activated during room-temperature deformation. Consequently, a slightly decreased proof strength but tripled elongation is shown at room temperature. Unexpectedly, large enhancement in creep resistance is detected after the co-alloying of Zn and Ca and the minimum creep rate is reduced by 10 to 20 times in the BZX621 alloy. Stress exponent n = 4–5 indicates that the creep is a dislocation-climb controlled type. Post-mortem characterization on microstructure shows slip of dislocation 〈c + a〉 are also largely found in B6 as well as BZX621 alloy and cross-slip is detected more severe in B6 alloy. Dynamic segregation and precipitation are also seen in both alloys. Bi-clusters are seen dispersive across the grains in B6 and so did the PFZs that could undermine creep resistance at the grain boundaries. By contrast, Zn-rich needle-like precipitates are developed at most “ends” of 〈c + a〉 dislocations, which would hinder the further dislocation motions and thus improve the creep resistance. First-principles calculations were adopted and the results show that the thermal stability and thermomechanical properties of Mg2Bi2Ca are much better than that of Mg3Bi2. Stacking faults energy is lowered down with the co-addition of Ca and Zn, which could inhibit the rate of dislocation climb and cross-slip. As a result, the improved creep resistance is obtained in the Mg-Bi-Zn-Ca alloys. Microstructural and controlling mechanism changes by thermal activation result in the unexpected enhancement in creep resistance with decreased room-temperature proof strength after co-addition. These findings could contribute to the development and optimization of creep-resistant Mg alloys in the future.

Achieving superior grain refinement efficiency for Al–Si casting alloys through a novel Al–La–B grain refiner

Conventional Al–Ti–B and Al–Ti–C refiners fail to refine Al–Si casting alloys with high Si content due to the well-known “Si-poisoning” effect. Developing a novel grain refiner with superior grain refinement efficiency for Al–Si casting alloys is the research focus in recent years. In this work, a superior anti Si-poisoning α-Al grain refiner Al–2La–1B alloy with fine LaB6 particles was successfully fabricated via the aluminum melt reaction method. The microstructural evolution, grain refinement performance and refinement mechanisms of the Al–2La–1B alloy were comprehensively investigated based on the experiment results and first-principles calculations. The currently designed Al–2La–1B refiner presents supreme grain refinement efficiency on Al–Si casting alloys. The average grain size of Al–7Si alloy inoculated with 0.5% Al–2La–1B alloy can be refined to 67 ± 5 μm. The superior grain refinement performance can be attributed to the presence of fine LaB6 particles in the refiner. These particles are highly stable in Al–Si alloy melt and can directly act as the potent nucleation sites for α-Al due to the small lattice misfit and low interfacial energy. Moreover, the nucleation potency of the LaB6 particles will not be influenced by the solute Si element. Our work provides an effective strategy for designing a superior α-Al grain refiner for Al–Si casting alloys.

Reciprocating dry sliding friction and wear behavior of B319 aluminum alloy-graphene composites

In the current study, the B319 aluminum (Al) alloy-graphene composites were fabricated using a stir-casting process, and the composites' tribological behavior was examined under dry sliding conditions. The B319–0.3 wt% graphene exhibited ∼42% and ∼52% higher friction and wear resistance than the baseline B319 alloy. Both friction and wear resistance of the B319 alloy deteriorated at higher graphene contents (0.5 and 0.7 wt%), indicating the best tribological performance was achieved with 0.3 wt% graphene addition. The wear in the base alloy primarily occurred by mechanically mixed layer (MML) delamination via subsurface crack propagation, while the wear in the B319 - 0.3 wt% graphene composite was driven by MML fragmentation, accompanied by adhesive, oxidative, and abrasive wear mechanisms.

Effect of graphene on the microstructure, thermal conductivity, and tribological behavior of cast B319 Al alloy

In this research, the effect of adding 0.1 – 0.7 wt% of graphene on the microstructure, hardness, thermal conductivity, and tribological response of cast B319 Al alloy was investigated. Addition of 0.1 wt% graphene increased the hardness of cast B319 alloy from 77 to 92 HV, which was the result of grain refinement and the modification of the Si phase. At 0.3 wt% graphene, the composite achieved optimal wear resistance, as the average coefficient of friction (CoF) decreased from 0.42 to 0.20, a ∼52% reduction with respect to the base B319 alloy. Similarly, the average wear volume and specific wear rate of 0.3 wt% graphene composite showed a ∼36% (measured by weight loss) and ∼32% (measured by the laser microscopy) reduction compared to the base alloy. The improved wear resistance of the composite was attributed to its higher hardness caused by microstructural refinement, high stability of the mechanically mixed layer (MML), and the formation of a graphene-rich lubricating layer on the contact surfaces. The results obtained from this study on B319-graphene composites could pave the way for developing lightweight and high-performance wear-resistant components for next-generation automotive applications.

A comparative study of the amorphization of NiTi-B2 structure by anti-site defects

This paper reports a comparative study of the amorphization of B2 structure of near-equiatomic NiTi and three other equiatomic binary B2 alloy systems, including AlFe, CuZr and FeTi. The study was conducted by means of molecular dynamics simulation on the effects of anti-site defects within the B2 structure. It was found that anti-site defects cause severe random distortions to the B2 structures, lowering their crystalline ordering. Among the four B2 systems studied, equiatomic AlFe and FeTi cannot be fully amorphized by anti-site defects but NiTi and CuZr can become fully amorphous at above a threshold concentration of the defects, as compared to the structure of quenched liquid. It is also found that the threshold anti-site concentration for amorphization decreases with increasing temperature. In comparison between the two, NiTi is easier to be amorphized than CuZr by anti-site defects, both in terms of the threshold anti-site defect concentration required and the temperature range within which it is possible. These findings may help to explain the long-observed phenomenon of the easiness of equiatomic NiTi to become amorphous during cold working and the new observation of third element substitutional diffusion caused amorphization.

Understanding the formation mechanisms and stability of the Anti-Phase boundaries (APBs) in Al-Fe B2

Al-Fe B2 alloys (with ordered Body Centered Cubic lattice, BCC) are an example of high strength, brittle materials containing multiple crystal defects, such as dislocations, vacancies and Anti-Phase Boundaries (APB). Although latter were reported to play a major role in mechanisms influencing mechanical properties, reports on formation mechanisms of APBs are limited and contradictory. To close this gap in understanding, FexAl1−x alloys were studied in Transmission Electron Microscope (TEM). Changing the Long-Range Order, η, parameter (calculated using statistical thermodynamics according to the composition of the samples) from 1 (50 at% Fe, i.e., perfect order) to η = 0.53 (68 at% Fe) caused an increase in density of the <111> type dislocations. At η = 0.53 – APBs have started to form. These experimental results were in-line with Density Functional Theory calculations. Since above 68 at% Fe, D03-type structure has also formed in the B2 grains, its role in formation of the APBs was assessed. It was determined that these two phenomena are not related. Therefore, outcomes of current research are of general applicability to other B2 structures regardless existence of D03 or lack of such additional ordering. Furthermore, driven conclusions have a potential to impact the BCC-based High Entropy Alloys, where B2 is the matrix.

Tensile behavior of cast γ-TiAl alloys with varied boride morphologies

Boride particles of various sizes and morphologies were obtained by adjusting the boron content and solidification rate of castings in Ti–45Al–2Mn–2Nb alloys. The initial and deformation microstructures, as well as the tensile properties at 25 °C and 650 °C, were examined. Furthermore, the fracture behavior of the alloys and the influence of boride particle with different morphologies on the tensile properties were discussed. Boride particles are curved flaky in 0.5B alloys, and varied from straight rod/needle-like to curved ribbon-like with increasing cooling rates in 1B alloys. Abundant phase interfaces, along with the presence of growth stacking faults and lattice distortions, are prominently observed in curved flaky and ribbon-like boride particles. Conversely, straight boride particles exhibit better regularity, with fewer lattice distortions and a lower density of interfaces and stacking faults. At both 25 °C and 650 °C, samples containing flaky boride particles exhibit the highest yield strength but the lowest elongation, while samples containing rod/needle-like boride particles show the lowest yield strength but the highest elongation. Curved boride particles exhibited no deformation, while their interfaces with the matrix accumulated a significant volume fraction of dislocations. This accumulation of dislocations causes stress concentration and created sites for the initiation of cracks. Additionally, the larger surface area of flaky boride particles promotes the growth of larger cracks, thus reducing ductility. On the other hand, straight rod/needle-like particles underwent deformation, resulting in the formation of deformation stacking faults on (0001) of C32–TiB2 and (10 1‾) of B27–TiB, showing better deformation compatibility between the borides and matrix.

Magnetic properties and structure of the Fe63.5Mn10Cu1Nb3Si13.5B9 alloy nanocrystallized under tensile stresses

The influence of introduction of 10 at. % Mn for Fe in the classical Finemet (Fe73.5Cu1Nb3Si13.5B9) on its magnetic properties, magnetic anisotropy, and structure is studied after nanocrystallization annealing at 520°C with varying duration from 10 min to 4 h in the presence of tensile stresses (σ = 200 MPa) (SA) and without them (NA). It is established that in the Fe63.5Mn10Cu1Nb3Si13.5B9 alloy (Mn10-alloy), just as in the classical Finemet, SA results in the induction of transverse magnetic anisotropy, yet, the constant of induced magnetic anisotropy is decreased by a factor of 4. The coercivity of the Mn10-alloy grows with increasing annealing time upon both SA and NA, while that of Finemet virtually does not change. Unlike Finemet, in the Mn10-alloy, along with the α-Fe(Si, Mn) solid solution and Fe3Si phase, there form borides already after 10-min treatment. This results in the change in the volume fractions of structure components with a negative magnetostriction, α-Fe(Si, Mn) and Fe3Si, which are responsible for the induction of transverse magnetic anisotropy, and positive magnetostriction, FeB, Fe2B, Fe3B, and hence, most likely, causes decrease in the constant of IMA of the Mn10-alloy. Besides, unlike Finemet, the average grain size in the alloy with Mn increases with the time of annealing, which, together with the formation of borides, increases the coercivity.

Magnetic Properties and Structure of the Fe63.5Mn10Cu1Nb3Si13.5B9 Alloy Nanocrystallized in the Presence of Tensile Stresses

Magnetic Properties and Structure of the Fe63.5Mn10Cu1Nb3Si13.5B9 Alloy Nanocrystallized in the Presence of Tensile Stresses

Corrosion behaviors of Mg−39Pb−11.5Al−1B−0.4Sc alloy in 3.5 wt.% NaX (X=F, Cl, Br and I) solutions

Mg−39Pb−11.5Al−1B−0.4Sc alloy was prepared by melting method, and the corrosion behaviors and mechanisms in 3.5 wt.% NaX (X = F, Cl, Br, and I) solutions were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), polarization curve test, and electrochemical impedance spectroscopy (EIS). The results show that the phases of Mg−39Pb−11.5Al−1B alloy are α-Mg, Mg2Pb, Mg17Al12 and AlB2. The addition of Sc can refine the microstructure significantly. The corrosion resistance of Mg−39Pb−11.5Al−1B−0.4Sc alloy in NaX solutions is in the order of NaCl < NaBr < NaI < NaF. During the corrosion process in NaX (X=Cl, Br, and I) solutions, Mg is first dissolved, then Mg2Pb is dissolved, and finally Mg17Al12 is fallen off from matrix. The corrosion products of Mg and Mg2Pb are Mg(OH)2 and MgO, respectively.

Microstructure, Texture Evolution, and Aging Behavior of a Cold‐Rolled Ti–B20 Alloy

The microstructure, texture evolution, and aging behavior of a cold‐rolled (CR) Ti–B20 alloy are investigated in this work. The results show that the microstructure of the solution‐treated (ST) Ti–B20 alloy consists of equiaxed recrystallized grains and exhibits typical {001}&lt;110&gt; and {001}&lt;100&gt; textures. After cold rolling, the initial equiaxial grains are stretched along the rolling direction (RD), which can produce typical deformation textures of γ‐fiber {111}&lt;112&gt; and {111}&lt;110&gt; textures. For the CR samples after aging treatment, small amounts of needle‐like or spherical α‐phases preferentially precipitate in the grain boundaries of deformed β grains during aging treatment; many nanosized α‐phases uniformly precipitate in the grain boundaries and inside the β grains. A high dislocation density is generated in CR samples, promoting α‐phase nucleation, increasing the volume fraction, and decreasing the α‐phase size during aging treatment.

Phase stability and magnetic properties of B2 and L10 PtMn1-XFeX alloys: a cluster expansion and ab initio approach

MnPt-based alloys are promising new materials for magnetic recording and spintronic applications due to their interesting magnetic properties. The underlying thermodynamic properties are still unclear, despite numerous efforts to improve ferromagnetic stability through alloying. In this work, the phase stability of B2 and L10 PtMn1-xFex alloys is investigated using a combination of density functional theory (DFT) and Cluster Expansion (CE). CE model accuracy is evaluated against DFT data, where cross-validation scores were found to be reasonable. The CE generated 16 and 27 new structures on B2 and L10 PtMn1-xFex, respectively. The ground state line predicted 6 stable structures with negative formation energies for both B2 and L10 PtMn1-xFex alloys, suggesting thermodynamic stability. Furthermore, the magnetic strength of the ground state structures is evaluated using DFT.

Plastic TiZrHfCoNiCu high entropy alloy via stable B2 phase

(Ti, Zr, Hf)(Co, Ni, Cu) high entropy alloys (HEAs) have excellent properties such as high-temperature shape memory property and high yield strength that have attracted widespread attention in recent years, but their application has been limited due to the lack of plastic deformability. In this work, we examined the possibility of synthesizing a new HEA with good mechanical properties by controlling the formation ability of metastable amorphous (am) and B2 phases for Ti16.5Zr17Hf16.5Co16.5Ni16.5Cu17 HEA. The as-spun amorphous and [am＋B2] phase ribbons with good bending plasticity were formed. The mixed-phase ribbon exhibits higher tensile plasticity than the amorphous ribbon because of the easy generation of shear bands and the suppression of their propagation around the B2 phase. Besides, the B2 phase is formed for the cast rod with a diameter of 2 mm. The B2 rod exhibits compressive strength up to 2254 MPa and a plastic strain of about 5%. The B2 alloy rod also has high thermal stability and keeps good mechanical properties after annealing under 973 K for 1.8 ks. The high mechanical strength and good plasticity of the B2 HEA are due to the generations of deformation-induced dislocation and martensite B33 phase. The synthesis of the B2 HEA with excellent mechanical properties through the deformation-induced martensite transformation is promising for future structural material.

Enhanced magnetic properties of Ce17Fe76.5Co1Zr0.5B6 alloys by magnetic field heat treatment

In the present work, Ce17Fe76.5Co1Zr0.5B6 ribbons were prepared by a direct melt spinning method. The effects of chamber pressure and magnetic field annealing temperature on the magnetic properties and microstructures of the alloys were investigated. The grain size and content of Ce2Fe14B phase can be changed by adjusting the chamber pressure, and the optimal magnetic performance is obtained at 0.04 MPa. The magnetic properties can be influenced under magnetic field heat treatment. When the annealing temperature is lower than the Curie temperature, the refinement and a uniform distribution of the grains is obtained. The irreversible magnetic susceptibility curve reveals that magnetic field heat treatment enhances the exchange coupling interaction between grains of the Ce2Fe14B phase. When the magnetic field annealing temperature is 438 K, the alloy displays the optimal magnetic properties. Compared with the as-spun sample, the values of intrinsic coercivity (Hci), remanence (Br) and maximum energy product ((BH)max) increase by 3.4%, 9.8% and 18.7%, respectively. This work provides an effective approach by which to enhance the magnetic properties of Ce–Fe–B alloys.

Composition-dependent thermal equation of state of B2 Fe-Si alloys at high pressure

AbstractSolid iron-silicon alloys play an important role in planetary cores, especially for planets that formed under reducing conditions, such as Mercury. The CsCl (B2) structure occupies a considerable portion of the Fe-Si binary phase diagram at pressure and temperature conditions relevant for the core of Mercury, yet its thermodynamic and thermoelastic properties are poorly known. Here, we report in situ X-ray diffraction measurements on iron-silicon alloys with 7–30 wt% Si performed in laser-heated diamond-anvil cells up to ~120 GPa and ~3000 K. Unit-cell volumes of the B2 phase at high pressures and high temperatures have been used to obtain a composition-dependent thermal equation of state of this phase. In turn, the thermal equation of state is exploited to determine the composition of the B2 phase in hcp+B2 mixtures at 30–100 GPa and to place constraints on the hcp+B2/B2 phase boundary, determined to vary between ~13–18 wt% Si in the considered pressure and temperature range. The hcp+B2/B2 boundary of Fe-Si alloys is observed to be dependent on pressure but weakly dependent on temperature. Our results, coupled with literature data on liquid equations of state, yield an estimation of the density contrast between B2 solid and liquid under Mercury’s core conditions, which directly relates to the buoyancy of the crystallizing material. While the density contrast may be large enough to form a solid inner core by the gravitational sinking of B2 alloys in a Si-rich core, the density of the B2 solid is close to that of the liquid at solidus conditions for Si concentration approaching ~10 wt% Si.

Ordered structure and mechanical properties of ternary Sc0.5TM0.5B2 (TM = Ti, V, Zr) alloys under high pressure

The structural and mechanical properties of ScB2 and Sc0.5TM0.5B2 (TM = Ti, V, Zr) alloys are investigated in the pressure range of 0–150 GPa based on density functional theory. The ground state structures of ScB2 are screened out by structural substitution, and the P6/mmm is determined as the initial structure of alloying research according to structural stability. The structures of alloy generation and recognition (SAGAR) code combined with first-principles calculations selected the stable structures of Sc0.5TM0.5B2 (TM = Ti, V) and Sc0.5Zr0.5B2 alloys as ordered structure types Ⅰ and Ⅱ, respectively. The formation enthalpy, phonon dispersion and elastic constants demonstrate that Sc0.5TM0.5B2 (TM = Ti, V, Zr) alloys are thermodynamically, dynamically and mechanically stable. In the whole pressure range, the elastic moduli of Sc0.5TM0.5B2 (TM = Ti, V, Zr) increased significantly compared with ScB2. This indicates that the introduction of TM improves the mechanical properties of ScB2. The Vickers hardness (HV) of the ScB2 ground state is 42.4 GPa, and the HV of the Sc0.5TM0.5B2 (TM = Ti, V, Zr) alloys are increased to 47.8, 50.3 and 44.8 GPa, respectively. The electronic structures and chemical bonding reveal that the Sc0.5TM0.5B2 (TM = Ti, V, Zr) alloys have stronger B–B, B–TM covalent bonds, charge interaction, and higher valence electron density, which significantly improves the hardness. The results show that ScB2 and Sc0.5TM0.5B2 (TM = Ti, V, Zr) alloys are potential superhard multifunctional materials.